The present invention relates to methods of splicing or connecting optical fibers, to components employed in the fabrication of such splices and connections, and to the resulting article.
Systems employing optical fibers require means to effect the transfer of energy from one fiber to another without undue power loss. Some connectors position optical fibers in end-to-end relationship so that light emanating from one fiber endface is directed into the adjacent fiber endface. U.S. Pat. Nos. 4,763,970, 4,746,189 and 4,807,959 teach methods of effecting the end-to-end alignment of two optical fibers by inserting them into opposite ends of a capillary tube. The technician performing the connection attempts to bring the fiber endfaces into abutment using hand-eye coordination. An index matching substance such as an oil or a glue has been employed at the junction between the fibers to enhance the transfer of light therebetween. The basis for selection of such a substance has been its refractive index and its transparency. The refractive index should be equal to or sufficiently close in value to that of the fiber cores to reduce Fresnel losses. Heretofore, it has been thought that the index matching substance should be transparent in order to minimize the attenuation of light propagating through the thin layer of such substance which extends between the fiber endfaces.
Because of the small size of the fibers, it is difficult for the technician to see the endfaces coming into abutment. It has therefore been conventional practice to continue the inward movement of at least one of the fibers until it begins to buckle, thus ostensibly signifying the abutment of the fiber endfaces. Perhaps due to such factors as the small core diameter of single-mode fibers and the bend sensitivity thereof, an excessive amount of fiber buckling causes excessive connector attenuation. Another possible cause of high attenuation is the occurrence of an obstruction in the capillary tube which prevents fiber-to-fiber contact. When conventional transparent glue is employed, the obstruction may go unnoticed, and the technician may erroneously interpret fiber buckling as an indication of fiber-to-fiber contact.
To aid the technician in this task, some connectors employ a feedback process using power transmission. The craftsperson adjusts the fiber ends while watching a meter indicating the amount of power transmitted from one fiber to the other. The splice is completed when the technician ascertains that the minimum power loss has been achieved. That method requires the use of expensive equipment and the process of connecting the fibers to the measuring equipment is time consuming.
The optical fiber connector disclosed in U.S. Pat. No. 4,787,697 comprises an inner transparent frame containing means defining a fiber aligning groove and an outer transparent sleeve disposed around the frame. A magnifying lens above the frame allows the viewer to see a magnified view of that region of the connector where the optical fibers abut. In one embodiment, the fibers are disposed within a channel contained in the frame, a lid over the frame comprising the magnifying lens. In a second embodiment, the outer sleeve functions as the lens. Since the technician can more easily see the location of the fiber ends, the task of placing the fiber ends in proper position is made less difficult. That patent states that the use of such a magnification lens will increase the probability of obtaining optical connections with low power loss and will also reduce the number of chipped fiber endfaces caused by abruptly bringing the fibers together. The connector of that patent is complex in that it requires the manufacture and subsequent assembly of a plurality of parts.